Dynamic power amplifier backoff using headroom information

ABSTRACT

Systems and methodologies are described that facilitate mitigating effect of non-linear distortion from a power amplifier on a spectral mask margin. Power limit indications can be analyzed in scheduling mobile devices. Mobile devices with power limits can be scheduled on inner subbands. The power limits can be based at least in part on power amplifier headroom information. Other mobile devices can employ remaining portions of an allocated spectrum. Further, mobile devices can evaluate and establish a power amplifier backoff based upon the subband scheduling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.11/923,761 entitled “DYNAMIC POWER AMPLIFIER BACKOFF USING HEADROOMINFORMATION,” filed Oct. 25, 2007, which claims the benefit of U.S.Provisional Patent application Ser. No. 60/863,118 entitled “AT PAHEADROOM INFORMATION TO ENABLE DYNAMIC PA BACKOFF IN LBC FDD” which wasfiled Oct. 26, 2006. The entirety of the aforementioned application isherein incorporated by reference.

BACKGROUND

I. Field

The following description relates generally to wireless communications,and more particularly subband scheduling and power amplifier backoff.

II. Background

Wireless networking systems have become a prevalent means by which amajority of people worldwide have come to communicate. Wirelesscommunication devices have become smaller and more powerful in order tomeet consumer needs and to improve portability and convenience.Consumers have become dependent upon wireless communication devices suchas cellular telephones, personal digital assistants (PDAs) and the like,demanding reliable service, expanded areas of coverage and increasedfunctionality.

Generally, a wireless multiple-access communication system maysimultaneously support communication for multiple wireless terminals oruser devices. Each terminal communicates with one or more access pointsvia transmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the access points to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the access points.

Wireless systems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems.

Typically, each access point supports terminals located within aspecific coverage area referred to as a sector. A sector that supports aspecific terminal is referred to as the serving sector. Other sectors,not supporting the specific terminal, are referred to as non-servingsectors. Terminals within a sector can be allocated specific resourcesto allow simultaneous support of multiple terminals. However,transmissions by terminals in neighboring sectors are not coordinated.Consequently, transmissions by terminals at sector edges can causeinterference and degradation of in-sector terminal performance

SUMMARY

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements of allembodiments nor delineate the scope of any or all embodiments. Its solepurpose is to present some concepts of one or more embodiments in asimplified form as a prelude to the more detailed description that ispresented later.

According to an aspect, a method that mitigates non-linear distortion onspectral mask margin is described herein. The method can comprisescheduling a first group of at least one mobile device on an innersubband of an allocated spectrum based upon power amplifier headroominformation from the first group. The method can also include schedulinga subsequent group of at least one mobile device on a remaining portionof the allocated spectrum after scheduling the inner subband based uponpower amplifier headroom information from the subsequent group.

Another aspect relates to a wireless communications apparatus. Thewireless communications apparatus can include at least one processorconfigured to schedule at least one mobile device with power limits oninner subbands of a spectrum and scheduling at least one mobile devicewithout power limits on remaining portions of the spectrum, the powerlimits relate to power amplifier headroom information. The wirelesscommunications apparatus can also include a memory coupled to the atleast one processor.

Yet another aspect relates to a wireless communications apparatus thatenables dynamic power amplifier backoff. The wireless communicationsapparatus can comprise means for scheduling a first group of at leastone mobile device on an inner subband of an allocated spectrum based atleast in part on power amplifier headroom information from the firstgroup. The wireless communications apparatus can additionally includemeans for scheduling a subsequent group of at least one mobile device ona remaining portion of the allocated spectrum based at least in part onpower amplifier headroom information from the subsequent group as wellas means for selecting subbands based at least in part on poweramplifier headroom information.

Still another aspect relates to a computer program product, which canhave a computer-readable medium including code for causing at least onecomputer to schedule at least one mobile device with power limits oninner subbands of a spectrum. The code can also cause the at least onecomputer to schedule at least one mobile device without power limits onremaining portions of the spectrum, the power limits relate to poweramplifier headroom information.

In accordance with another aspect, an apparatus in a wirelesscommunication system can include a processor configured to schedule afirst group of at least one mobile device on an inner subband of anallocated spectrum based at least in part on power amplifier headroominformation from the first group. The processor can also be configuredto schedule a subsequent group of at least one mobile device on aremaining portion of the allocated spectrum based at least in part onpower amplifier headroom information from the subsequent group.Furthermore, the processor can be configured to select subbands based atleast part on power amplifier headroom information. Also, the apparatuscan include a memory coupled to the processor.

According to a further aspect, a method that facilitates dynamicallyadjusting power amplifier backoff is described herein. The method caninclude transmitting a periodic power headroom measurement correspondingto a maximum achievable transmit power. The method can also includeadvertising static differential power headroom corresponding to one ormore points of interest and receiving a subband assignment.

Another aspect relates to a wireless communications apparatus. Thewireless communications apparatus can include at least one processorconfigured to transmit a periodic power headroom measurementcorresponding to a maximum achievable transmit power and advertisestatic differential power headroom corresponding to one or more pointsof interest. The wireless communications apparatus can also include amemory coupled to the at least one processor.

Yet another aspect relates to a wireless communication apparatus thatmitigates non-linear distortion on spectral mask margin. The wirelesscommunications apparatus can comprise means for transmitting a periodicpower headroom measurement corresponding to a maximum achievabletransmit power for a broadband assignment. Moreover, the wirelesscommunications apparatus can comprise means for advertising staticdifferential power headroom corresponding to one or more points ofinterest.

Still another aspect relates to a computer program product, which canhave a computer-readable medium including code for causing at least onecomputer to transmit a periodic power headroom measurement correspondingto a maximum achievable transmit power. The code can also cause the atleast one computer to advertise static differential power headroomcorresponding to one or more points of interest and receive a subbandassignment.

In accordance with another aspect, an apparatus can be provided in awireless communication system including a processor configured totransmit a periodic power headroom measurement corresponding to amaximum achievable transmit power for a broadband assignment. Further,the processor can be configured to advertise static differential powerheadroom corresponding to one or more points of interest. Additionally,the apparatus can comprise a memory coupled to the processor.

To the accomplishment of the foregoing and related ends, the one or moreembodiments comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe one or more embodiments. These aspects are indicative, however, ofbut a few of the various ways in which the principles of variousembodiments may be employed and the described embodiments are intendedto include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system that facilitates dynamic poweramplifier backoff.

FIG. 2 is an illustration of an channel tree structure for supportingsubband scheduling.

FIG. 3 is an illustration of a wireless communication system inaccordance with various aspects set forth herein.

FIG. 4 is an illustration of an example wireless communications systemthat effectuates dynamic power amplifier backoff based upon subbandscheduling.

FIG. 5 is an illustration of a wireless communication system inaccordance with one or more aspects presented herein.

FIG. 6 is an illustration of an example methodology that facilitatessubband scheduling based upon consideration of power limitations.

FIG. 7 is an illustration of an example methodology that facilitatesadjusting a power amplifier backoff base upon a subband schedule.

FIG. 8 is an illustration of an example methodology that facilitatessignaling information over a reverse in connection with obtaining ascheduled subband assignment for transmissions.

FIG. 9 is an illustration of an example mobile device that facilitatesdetermining a power amplifier backoff value.

FIG. 10 is an illustration of an example system that facilitatesgenerating a subband schedule based upon power limitation information.

FIG. 11 is an illustration of an example wireless network environmentthat can be employed in conjunction with the various systems and methodsdescribed herein.

FIG. 12 is an illustration of an example system that facilitatesgenerating a subband schedule.

FIG. 13 is an illustration of an example system that facilitatestransmitting power headroom information.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more embodiments. It may be evident, however,that such embodiment(s) can be practiced without these specific details.In other instances, well-known structures and devices are shown in blockdiagram form in order to facilitate describing one or more embodiments.

As used in this application, the terms “component,” “module,” “system,”and the like are intended to refer to a computer-related entity, eitherhardware, firmware, a combination of hardware and software, software, orsoftware in execution. For example, a component can be, but is notlimited to being, a process running on a processor, a processor, anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running on acomputing device and the computing device can be a component. One ormore components can reside within a process and/or thread of executionand a component can be localized on one computer and/or distributedbetween two or more computers. In addition, these components can executefrom various computer readable media having various data structuresstored thereon. The components can communicate by way of local and/orremote processes such as in accordance with a signal having one or moredata packets (e.g., data from one component interacting with anothercomponent in a local system, distributed system, and/or across a networksuch as the Internet with other systems by way of the signal).

Furthermore, various embodiments are described herein in connection witha mobile device. A mobile device can also be called a system, subscriberunit, subscriber station, mobile station, mobile, remote station, remoteterminal, access terminal, user terminal, terminal, wirelesscommunication device, user agent, user device, or user equipment (UE). Amobile device can be a cellular telephone, a cordless telephone, aSession Initiation Protocol (SIP) phone, a wireless local loop (WLL)station, a personal digital assistant (PDA), a handheld device havingwireless connection capability, computing device, or other processingdevice connected to a wireless modem. Moreover, various embodiments aredescribed herein in connection with a base station. A base station canbe utilized for communicating with mobile device(s) and can also bereferred to as an access point, Node B, or some other terminology.

Moreover, various aspects or features described herein can beimplemented as a method, apparatus, or article of manufacture usingstandard programming and/or engineering techniques. The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media. Forexample, computer-readable media can include but are not limited tomagnetic storage devices (e.g., hard disk, floppy disk, magnetic strips,etc.), optical disks (e.g., compact disk (CD), digital versatile disk(DVD), etc.), smart cards, and flash memory devices (e.g., EPROM, card,stick, key drive, etc.). Additionally, various storage media describedherein can represent one or more devices and/or other machine-readablemedia for storing information. The term “machine-readable medium” caninclude, without being limited to, wireless channels and various othermedia capable of storing, containing, and/or carrying instruction(s)and/or data.

The techniques described herein can be used for various wirelesscommunication systems such as multiple-access communication systems,broadcast systems, wireless local area networks (WLANs), etc. The terms“systems” and “networks” are often used interchangeably. Amultiple-access system can utilize a multiple-access scheme such as CodeDivision Multiple Access (CDMA), Time Division Multiple Access (TDMA),Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA),Single-Carrier FDMA (SC-FDMA), etc. A multiple-access system can alsoutilize a combination of multiple-access schemes, e.g., one or moremultiple-access schemes for the downlink and one or more multiple-accessschemes for the uplink.

OFDMA utilizes Orthogonal Frequency Division Multiplexing (OFDM), whichis a multi-carrier multiplexing scheme. SC-FDMA can utilize LocalizedFrequency Division Multiplexing (LFDM), Interleaved FDM (IFDM), EnhancedFDM (EFDM), etc., which are different single-carrier multiplexingschemes that are collectively referred to as Single-Carrier FDM(SC-FDM). OFDM and SC-FDM partition the system bandwidth into multiple(K) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier can be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. LFDM transmits data on continuoussubcarriers, IFDM transmits data on subcarriers that are distributedacross the system bandwidth, and EFDM transmits data on groups ofcontinuous subcarriers.

OFDM has certain desirable characteristics, including the ability tocombat multipath effects that are prevalent in a terrestrialcommunication system. However, a major drawback with OFDM is a highpeak-to-average power ratio (PAPR) for an OFDM waveform, i.e., the ratioof the peak power to the average power for the OFDM waveform can behigh. The high PAPR results from possible in-phase (or coherent)addition of all the subcarriers when they are independently modulatedwith data. The high PAPR for the OFDM waveform is undesirable and candegrade performance. For example, large peaks in the OFDM waveform cancause a power amplifier to operate in a highly non-linear region orpossibly clip, which can then cause intermodulation distortion and otherartifacts that can degrade signal quality. To avoid non-linearity, thepower amplifier can be operated with backoff at an average power levelthat is lower than the peak power level. By operating the poweramplifier with backoff from peak power, where the backoff can range from4 to 7 dB in one example, the power amplifier can handle large peaks inthe waveform without generating excessive distortion.

SC-FDM (e.g., LFDM) has certain desirable characteristics such asrobustness against multipath effects, similar to OFDM. Furthermore,SC-FDM does not have a high PAPR since modulation symbols are sent inthe time domain with SC-FDM. The PAPR of an SC-FDM waveform isdetermined by the signal points in the signal constellation selected foruse (e.g., M-PSK, M-QAM, etc). However, the time-domain modulationsymbols in SC-FDM are prone to intersymbol interference due to anon-flat communication channel. Equalization can be performed on thereceived symbols to mitigate the deleterious effects of intersymbolinterference.

In an aspect, OFDM and SC-FDM (e.g., LFDM) can be used for transmissionon a given link (e.g., uplink). In general, link efficiency of an OFDMwaveform exceeds that of an SC-FDM waveform. The higher link efficiencyof OFDM is offset by a larger power amplifier backoff for OFDM thanSC-FDM. SC-FDM thus has a low PAPR advantage over OFDM. For UEs withhigh signal-to-noise ratios (SNRs), the link level gain of OFDM canexceed the PAPR advantage of SC-FDM. By utilizing both OFDM and SC-FDM,the system can benefit from the higher link efficiency of OFDM for highSNR scenarios as well as the PAPR advantage of SC-FDM for low SNRscenarios.

In general, any SC-FDM scheme can be used jointly with OFDM.Furthermore, OFDM and SC-FDM can be jointly used for the uplink, or thedownlink, or both the uplink and downlink. For clarity, much of thefollowing description is for joint use of OFDM and LFDM on the uplink.

Referring now to FIG. 1, illustrated is a block diagram of a system 100that provides dynamic power amplifier backoff. System 100 includes atleast one base station 102 and at least one mobile device 104 supportedby a sector of base station 102. The term sector can refer to a basestation and/or an area covered by a base station, depending on context.A single base station and mobile device are illustrated for simplicity.However, system 100 can include multiple base stations and mobiledevices. Base station 102 can explicitly control the subband schedule ofmobile device 104. Subband scheduling enables multi-user diversity gainsby scheduling mobile devices adaptively over limited regions of thesystem frequency band according to channel conditions, among otherthings. The subband size can provide enough frequency diversity toprevent performance degradation for fast moving mobile devices as wellas degradation in sector throughput with equal grade of servicescheduling. Small subbands can also result in loss of trunkingefficiency of subband scheduling (e.g., the smaller the subbands, theless candidate mobile devices per subband to choose from). Though insome cases a scheduling algorithm, such as those described herein, canschedule assignments on a subband basis (e.g., one or more subbands),assignments can be in other units as well, such as one or more basenodes as described below.

Turning briefly to FIG. 2, illustrated is an exemplary channel tree withlocal hopping. A mobile device, scheduled within a certain subband andhaving a bandwidth assignment less than the entire subband, can hoplocally across the subband to maximize channel interference diversity.In FIG. 2, each base node can map to a number of contiguous tones infrequency (e.g., 16 as shown). A collection of eight base nodes maps toa subband, which consists of 128 contiguous tones. Within the subband,groups of 16 tones (e.g., the base nodes) can hop in a pseudo-randommanner. In addition to the subband scheduling mode, diversity mode canbe beneficial. A sector can serve predominantly fast moving users (e.g.,a sector cover a highway). In such cases, base nodes of the channel canhop across the entire band.

Referring back to FIG. 1, to support subband scheduling, a mobile device104 can provide feedback about forward link channel properties relativeto different subbands to the base station 102, in one example. Theamount of feedback can balance gains in forward link performance, forexample, due to subband scheduling versus the reverse link overheadcaused by feedback channels. A proper tradeoff depends on the load ofreverse link control channel which, besides subband scheduling feedback,can carry other reverse link control information.

According to one aspect of the subject disclosure, mobile device 104sends power limit information to base station 102. Base station 102employs the received power limit information to schedule mobile device104 on a subband. Power limit information can include informationrelated to power amplifier (PA) size and/or capabilities of mobiledevice 104. Moreover, power limit information can include differentpower levels that can be utilized for different types of assignments.For example, mobile device 104 can have one or more power levelsavailable in an inner subband while having one or more disparate powerlevels available on an edge subband. The mobile device 104 can alsoreport the maximum power it can achieve if its assignment spans theentire bandwidth, an inner subband, and/or a single base node, forexample. In addition, the information can convey the effect ofinterference constraints, if any. Furthermore, power limit informationcan comprise location within a given sector or cell and/or locationinformation relative to more than one sector or cell. Additionally, thepower limit information transmitted by mobile device 104 can include acarrier-to-interference parameter experienced by mobile device 104.While FIG. 1 depicts mobile device 104 transmitting power limitinformation to base station 102, it is to be appreciated that basestation 102 can infer such information from its link and communicationswith mobile device 104. For example, base station 102 can evaluate areceived power level or received feedback to infer any power constraintimposed upon mobile device 104.

Base station 102 employs the power limit information to schedule mobiledevice 104 on subbands available to system 100. In accordance with oneaspect of the subject disclosure, base station 102 can schedule powerlimited mobile devices predominantly on inner subbands. Mobile deviceswithout power limitations can be scheduled on the remaining spectrum. Inan example, base station 102 can consider power limitations of mobiledevice 104 in addition to channel selectivity across subbands whenselecting subbands. Moreover, base station 102 can transmit scheduleinformation to mobile device 104 indicating the subband to be employedby mobile device 104.

Referring now to FIG. 3, a wireless communication system 300 isillustrated in accordance with various embodiments presented herein.System 300 comprises a base station 302 that can include multipleantenna groups. For example, one antenna group can include antennas 304and 306, another group can comprise antennas 308 and 310, and anadditional group can include antennas 312 and 314. Two antennas areillustrated for each antenna group; however, more or fewer antennas canbe utilized for each group. Base station 302 can additionally include atransmitter chain and a receiver chain, each of which can in turncomprise a plurality of components associated with signal transmissionand reception (e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.), as will be appreciated by one skilledin the art.

Base station 302 can communicate with one or more mobile devices such asmobile device 316 and mobile device 322; however, it is to beappreciated that base station 302 can communicate with substantially anynumber of mobile devices similar to mobile devices 316 and 322. Mobiledevices 316 and 322 can be, for example, cellular phones, smart phones,laptops, handheld communication devices, handheld computing devices,satellite radios, global positioning systems, PDAs, and/or any othersuitable device for communicating over wireless communication system300. As depicted, mobile device 316 is in communication with antennas312 and 314, where antennas 312 and 314 transmit information to mobiledevice 316 over a forward link 318 and receive information from mobiledevice 316 over a reverse link 320. Moreover, mobile device 322 is incommunication with antennas 304 and 306, where antennas 304 and 306transmit information to mobile device 322 over a forward link 324 andreceive information from mobile device 322 over a reverse link 326. In afrequency division duplex (FDD) system, forward link 318 can utilize adifferent frequency band than that used by reverse link 320, and forwardlink 324 can employ a different frequency band than that employed byreverse link 326, for example. Further, in a time division duplex (TDD)system, forward link 318 and reverse link 320 can utilize a commonfrequency band and forward link 324 and reverse link 326 can utilize acommon frequency band.

Each group of antennas and/or the area in which they are designated tocommunicate can be referred to as a sector of base station 302. Forexample, antenna groups can be designed to communicate to mobile devicesin a sector of the areas covered by base station 302. In communicationover forward links 318 and 324, the transmitting antennas of basestation 302 can utilize beamforming to improve signal-to-noise ratio offorward links 318 and 324 for mobile devices 316 and 322. Also, whilebase station 302 utilizes beamforming to transmit to mobile devices 316and 322 scattered randomly through an associated coverage, mobiledevices in neighboring cells can be subject to less interference ascompared to a base station transmitting through a single antenna to allits mobile devices. According to an example, system 300 can be amultiple-input multiple-output (MIMO) communication system. Further,system 300 can utilize any type of duplexing technique to dividecommunication channels (e.g., forward link, reverse link . . . ) such asFDD, TDD, and the like.

Turning now to FIG. 4, illustrated is a wireless communications system400 that effectuates subband scheduling based upon considerations onpower limitations. System 400 includes a base station 402 thatcommunicates with a mobile device 404 (and/or any number of disparatemobile devices (not shown)). Base station 402 can transmit informationto mobile device 404 over a forward link channel; further base station402 can receive information from mobile device 404 over a reverse linkchannel. Moreover, system 400 can be a MIMO system.

System 400 employs a mitigation technique that reduces effect ofnon-linear distortion on spectrum mask margin. Non-linear distortionrelates to the phenomenon of a non-linear relationship between input andoutput of, for example, an electronic device. According to one aspect,the non-linear relationship concerned relates to a power amplifier.

Mobile device 404 can include a power limit indicator 410, backoffevaluator 412 and a power amplifier 414. Power limit indicator 410 ofmobile device 404 determines a power limitation indication that reflectspower constraints imposed upon mobile device 404. Mobile device 404transmits the power limitation indication to base station 402. It is tobe appreciated that base station 402 can infer such information from itslink and communications with mobile device 404 as well. For example,base station 402 can evaluate a received power level or receivedfeedback to determine a power constraint imposed upon mobile device 404.The power limitation indication can include information related to poweramplifier size or capabilities of mobile device 404. In addition, thepower limit indicator 410 can convey the effect of interferenceconstraints, if any. Furthermore, power limitation information cancomprise a location within a given sector or cell and/or locationinformation relative to more than one sector or cell. Additionally, thepower limit information transmitted by mobile device 404 can include acarrier-to-interference parameter experienced by mobile device 404.

Base station 402 receives the power limitation indication from mobiledevice 404 and employs the indication to determine subband scheduling.Base station 402 includes a subband selector 406 and a subband scheduler408. Subband selector 406 selects a subband based upon considerations ofthe power limitation indication of mobile device 404 and channelselectivity across subbands. Subband scheduler 408 schedules mobiledevice 404 and other mobile devices served by base station 402. Inaccordance with an aspect of the subject disclosure, subband scheduler408 schedules mobile devices with power limitations predominantly on theinner subbands. For example, high quality of service (QoS) users with alimited power amplifier size at a sector or cell edge can be scheduledon the inner subbands. Best effort users at sector or cell edge that arenot constrained by interference control (e.g., users' transmit power isnot limited by a busy bit from adjacent sectors) can also be scheduledon the inner subbands of the spectrum allocation. Further, subbandscheduler 408 can schedule mobile devices without power limitations onthe remaining spectrum. For example, best efforts users at sector orcell edge that are constrained by interference control (e.g., users'transmit power limited by a busy bit from adjacent sectors) can bescheduled on the remaining portions of the spectrum after schedulingpower limited users. In addition, users with large power amplifier sizescan be scheduled on the remaining spectrum allocated as well as userswith high carrier-to-interference (C/I) ratios. Users with high C/I canonly marginally benefit from a further increase in C/I that can resultfrom being scheduled on the middle regions of the allocated spectrum inone example.

Inner subbands are subbands away from the edges of spectrum allocationor total bandwidth. Out-of-band emissions are emissions on a frequencyor frequencies immediately outside and/or at some distance from theallocated bandwidth resulting from a modulation process. Out-of-bandemission level depends on total bandwidth spanned by an assignment andproximity of this span to an edge of spectrum allocation or maximumbandwidth of the system. Typically, the larger the assignment span(e.g., wide assignment), the higher the out-of-band emission level willbe. In addition, an assignment farther away from the edge results in alower out-of-band emission level. Out-of-band emission level can bemeasured as a function of total power over 1 MHz adjacent to the channelallocation. According to an example, total transmit power integratedover 1 MHz should not exceed −13 dBm. Additionally, for a typicallyaverage transmitted power of 23 dBm, a spectral mask requiresapproximately 30 dB attenuation in the adjacent 1 MHz.

A spectrum mask margin is defined as a difference between an allowedemission level and an actual emission level. Spectrum mask margin,L_(mask) can be given by the following:

$L_{mask} = {10*{\log_{10}\left( {\frac{\int{{S(f)}{f}}}{\int_{1{\; \;}{MHz}}{{S(f)}{f}}}\frac{P_{mask}}{P_{TX}}} \right)}}$

Pursuant to this illustration, P_(mask) can be the mask limit. Accordingto an example, P_(mask) should not exceed −13 dBm. P_(TX) can representthe total transmitted power. S(f) can represent the power spectraldensity at a power amplifier output, for example, where the quantity∫S(f)df can represent the power within the frequency band over which theintegral is taken. The quantity

∫_(1  MHz)S(f)f

can be the power over the 1 MHz adjacent to the channel allocation, forexample. A positive value indicates a margin between the allowed and theactual emission level. A negative value indicates the allowed emissionlevel is exceeded.

Mobile devices 404 have an adequate margin in an edge subband in both anOFDMA and LFDMA system if the mobile devices 404 employ a large backoffor are given a small assignment. In the situation with mobile devices404 employing small backoff, OFDMA devices experience a negative marginwith medium and large assignments while LFDMA users experience a smallpositive margin with a medium assignment. For users scheduled on amiddle or inner subband, the users experience a positive margin at lowbackoff in both OFDMA system and LFDMA systems. By scheduling users in amiddle subband, both OFDMA and LFDMA have a sufficient spectral maskmargin even at a 0 dB backoff indicating that both can operate at thatlow backoff. Accordingly, the PAPR disadvantage of OFDMA does not affectits power efficiency relative to LFDMA when users are scheduled awayfrom the edge of spectrum allocation.

Base station 402 can transmit assignment and scheduling information tomobile device 404. Mobile device 404 includes backoff evaluator 412 todetermine a backoff for power amplifier 414 based upon the schedulinginformation. In the situation where the scheduling information receivedby mobile device 404 indicates a medium or large assignment scheduled inan edge subband, backoff evaluator 412 can determine a large backoff.Typically, this backoff can be about 2 dB greater for OFDMA systems thanfor LFDMA systems to maintain a similar margin to the spectral mask.However, if subband scheduler 408 indicates mobile device is scheduledon a middle or interior subband, backoff evaluator 412 can determine alow backoff, for example, that is sufficient to maintain an adequatemarking to the spectral mask. According to an aspect, backoff evaluator412 can adjust the power amplifier 414 to employ a lower backoff (e.g.,a higher transmit power) when mobile device 404 is scheduled on an innersubband. When scheduled on an edge subband, power amplifier 414 canoperate at a higher backoff (e.g., a lower transmit power). In addition,the width of the assignment can be taken into account. For example, whenmobile device 404 is scheduled over 16 contiguous carriers (e.g., onebase node) only, in one example, out-of-band emissions are low as theassignment is contiguous and spans a narrow portion of total bandwidth.In this situation, a low backoff and high transmit power can betolerated.

According to an example, the power limit indicator 410 can compriseand/or determine power amplifier headroom information for the mobiledevice 404; the power amplifier headroom information relates to amaximum achievable transmit and/or receive power for the mobile device404, in one example. This information can be transmitted to the basestation 402 for calculating power amplifier headroom information, forexample; the power amplifier headroom information relates to a maximumachievable receive power for the base station 402 corresponding to themaximum achievable transmit power for the mobile device 404. This can becalculated for a given point of interest or potential broadbandassignment, for example, such as for the edge of a subband, an innersubband, and/or for a single base node (as described in reference toFIG. 2, for example). According to an example, the information can betransmitted to the base station 402 from the mobile device 404periodically via an out-of-band report (e.g., over a dedicated controlchannel) and/or an in-band report (e.g., as part of a data packet, suchas within a media access control (MAC) header thereof), such as during areverse link channel assignment and/or the like. This information can befor an actual broadband assignment, in one example. Moreover, the mobiledevice 404 can advertise static differential power headroom informationcorresponding to potential broadband assignments and/or points ofinterest as previously listed; it is to be appreciated that thisinformation can remain relatively static over time. The base station402, in this regard can compute the power headroom related to a type ofbroadband assignment or point of interest by adding the correspondingstatic differential power headroom to the corresponding periodicallyreported power headroom of the actual broadband assignment. The subbandcan be selected by the subband selector 406 and/or scheduled by thesubband scheduler 408 based at least in part on this information, forexample.

Referring now to FIG. 5, a wireless communication system 500 inaccordance with various aspects presented herein is illustrated. System500 can comprise one or more access points 502 that receive, transmit,repeat, etc., wireless communication signals to each other and/or to oneor more terminals 404. Each base station 502 can comprise multipletransmitter chains and receiver chains, e.g., one for each transmit andreceive antenna, each of which can in turn comprise a plurality ofcomponents associated with signal transmission and reception (e.g.,processors, modulators, multiplexers, demodulators, demultiplexers,antennas, etc.). Terminals 504 can be, for example, cellular phones,smart phones, laptops, handheld communication devices, handheldcomputing devices, satellite radios, global positioning systems, PDAs,and/or any other suitable device for communicating over wireless system500. In addition, each terminal 504 can comprise one or more transmitterchains and a receiver chains, such as used for a multiple input multipleoutput (MIMO) system. Each transmitter and receiver chain can comprise aplurality of components associated with signal transmission andreception (e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.), as will be appreciated by one skilledin the art.

As illustrated in FIG. 5, each access point provides communicationcoverage for a particular geographic area 506. The term “cell” can referto an access point and/or its coverage area, depending on context. Toimprove system capacity, an access point coverage area can bepartitioned into multiple smaller areas (e.g., three smaller areas 508A,508B and 508C). Each smaller area is served by a respective basetransceiver subsystem (BTS). The term “sector” can refer to a BTS and/orits coverage area depending upon context. For a sectorized cell, thebase transceiver subsystem for all sectors of the cell is typicallyco-located within the access point for the cell.

Terminals 504 are typically dispersed throughout system 500. Eachterminal 504 can be fixed or mobile. Each terminal 504 can communicatewith one or more access points 502 on the forward and reverse links atany given moment.

For a centralized architecture, a system controller 510 couples accesspoints 502 and provides coordination and control of access points 502.For a distributed architecture, access points 502 can communicate withone another as needed. Communication between access points via systemcontroller 510 or the like can be referred to as backhaul signaling.

The techniques described herein can be used for a system 500 withsectorized cells as well as a system with un-sectorized cells. Forclarity, the following description is for a system with sectorizedcells. The term “access point” is used generically for a fixed stationthat serves a sector as well as a fixed station that serves a cell. Theterms “terminal” and “user” are used interchangeably, and the terms“sector” and “access point” are also used interchangeably. A servingaccess point/sector is an access point/ sector with which a terminalcommunicates. A neighbor access point/sector is an access point/sectorwith which a terminal is not in communication.

Referring to FIGS. 6-8, methodologies relating to reverse link poweradjustment based upon broadcasted interference information areillustrated. While, for purposes of simplicity of explanation, themethodologies are shown and described as a series of acts, it is to beunderstood and appreciated that the methodologies are not limited by theorder of acts, as some acts can, in accordance with one or moreembodiments, occur in different orders and/or concurrently with otheracts from that shown and described herein. For example, those skilled inthe art will understand and appreciate that a methodology couldalternatively be represented as a series of interrelated states orevents, such as in a state diagram. Moreover, not all illustrated actscan be required to implement a methodology in accordance with one ormore embodiments.

Turning to FIG. 6, illustrated is a methodology 600 that facilitatesscheduling mobile devices on subbands based upon considerations of powerlimit indicators in a wireless communication system. At referencenumeral 602, power limit indicators are received. Power limit indicatorscan include, among other things, information related to power amplifiersize or capabilities, a presence of interference constraints, if any, alocation within a given sector or cell, and/or location informationrelative to more than one sector or cell and a carrier-to-interferenceparameter experienced by a mobile device. At reference numeral 604,subbands are selected. The selection can be based upon at least one of apower limitation of mobile devices, channel selectivity across subband,and/or the like. At reference numeral 606, mobile devices are scheduledon subbands. Scheduling is based upon the received power limitindicators. For example, power limited users are scheduled on innersubbands while mobile devices without power limitations are scheduled onthe remaining portions of the spectrum allocation.

Turning to FIG. 7, illustrated is a methodology 700 that facilitatesadjusting power amplifier backoff based upon considerations of powerlimitations and subband scheduling information. At reference numeral702, power limitation indicators are transmitted, to a base station oraccess point for example. Power limit indicators can include, amongother things, information related to power amplifier size orcapabilities, a presence of interference constraints, if any, a locationwithin a given sector or cell and/or location information relative tomore than one sector or cell, and a carrier-to-interference parameterexperienced by a mobile device or access terminal. At reference numeral704, subband scheduling information is received. Subband schedulinginformation can include the subbands within an allocated spectrum to beemployed. For example, the scheduling information can indicate thatinner subbands are to be utilized. At reference numeral 706, thescheduling information is employed to evaluate a power amplifier backoffto be applied to a power amplifier. For example, if the schedulinginformation indicates utilization of an inner subband, a low backoff canbe determined Conversely, if the information indicates that an edgesubband is to be utilized, a high backoff can be determined such that anadequate spectral mask margin is maintained.

With reference to FIG. 8, illustrated is a methodology 800 thatfacilitates signaling information over an uplink in connection withobtaining a scheduled subband assignment for transmission. At 802,information including power limitations can be signaled to a basestation over a reverse link. According to an example, the informationcan be sent as part of a request; however, the claimed subject matter isnot so limited. At 804, a subband assignment can be obtained from thebase station, where the assignment can be generated at least in partupon the signaled information. For example, the signaled information canbe employed by the base station to determine one or more spectral maskmargins for users signaling information. Further, the base station canconsider such margins in connection with yielding the subbandassignment. At 806, traffic can be transmitted on the reverse link byemploying the subband assignment. Thus, reverse link transmission can beeffectuated at a frequency, time, rate, etc. specified in the subbandassignment, for example.

It will be appreciated that, in accordance with one or more aspectsdescribed herein, inferences can be made regarding determining powerlimitations, determining which users to schedule on inner subbands,determining appropriate power amplifiers backoffs, etc. As used herein,the term to “infer” or “inference” refers generally to the process ofreasoning about or inferring states of the system, environment, and/oruser from a set of observations as captured via events and/or data.Inference can be employed to identify a specific context or action, orcan generate a probability distribution over states, for example. Theinference can be probabilistic—that is, the computation of a probabilitydistribution over states of interest based on a consideration of dataand events. Inference can also refer to techniques employed forcomposing higher-level events from a set of events and/or data. Suchinference results in the construction of new events or actions from aset of observed events and/or stored event data, whether or not theevents are correlated in close temporal proximity, and whether theevents and data come from one or several event and data sources.

According to an example, one or more methods presented above can includemaking inferences pertaining to scheduling mobile devices on subbands ofan allocated spectrum based at least in part upon considerations ofpower limitation information. By way of further illustration, aninference can be made related to determining a power amplifier backoffbased upon consideration of a subband schedule. It will be appreciatedthat the foregoing examples are illustrative in nature and are notintended to limit the number of inferences that can be made or themanner in which such inferences are made in conjunction with the variousembodiments and/or methods described herein.

FIG. 9 is an illustration of a mobile device 900 that facilitatesadjusting reverse link power based upon considerations of broadcastedinterference information. Mobile device 900 comprises a receiver 902that receives a signal from, for instance, a receive antenna (notshown), and performs typical actions thereon (e.g., filters, amplifies,downconverts, etc.) the received signal and digitizes the conditionedsignal to obtain samples. Receiver 902 can be, for example, an MMSEreceiver, and can comprise a demodulator 904 that can demodulatereceived symbols and provide them to a processor 906 for channelestimation. Processor 906 can be a processor dedicated to analyzinginformation received by receiver 902 and/or generating information fortransmission by a transmitter 916, a processor that controls one or morecomponents of mobile device 900, and/or a processor that both analyzesinformation received by receiver 902, generates information fortransmission by transmitter 916, and controls one or more components ofmobile device 900.

Mobile device 900 can additionally comprise memory 908 that isoperatively coupled to processor 906 and that can store data to betransmitted, received data, information related to available channels,data associated with analyzed signal and/or interference strength,information related to an assigned channel, power, rate, or the like,and any other suitable information for estimating a channel andcommunicating via the channel. Memory 908 can additionally storeprotocols and/or algorithms associated with estimating and/or utilizinga channel (e.g., performance based, capacity based, etc.).

It will be appreciated that the data store (e.g., memory 908) describedherein can be either volatile memory or nonvolatile memory, or caninclude both volatile and nonvolatile memory. By way of illustration,and not limitation, nonvolatile memory can include read only memory(ROM), programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable PROM (EEPROM), or flash memory. Volatile memorycan include random access memory (RAM), which acts as external cachememory. By way of illustration and not limitation, RAM is available inmany forms such as synchronous RAM (SRAM), dynamic RAM (DRAM),synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhancedSDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).The memory 908 of the subject systems and methods is intended tocomprise, without being limited to, these and any other suitable typesof memory.

Processor 906 is further operatively coupled to a power limit indicator910 that determines power limitations for mobile device 900. The powerlimitations can include information related to power amplifier size orcapabilities of mobile device 900. In addition, the indicator can conveythe effect of interference constraints, if any. Furthermore, powerlimitation information can comprise a location within a given sector orcell and/or location information relative to more than one sector orcell. Additionally, the power limit information transmitted by mobiledevice 902 can include a carrier-to-interference parameter experiencedby mobile device 902. Power limit indicator 910 transmits the powerlimitations to a base station or access point through a transmitter 916.Additionally, receiver 902 is coupled to a backoff evaluator that canutilize subband scheduling information received from a base station oraccess point to determine an appropriate backoff for a power amplifierof mobile device 900. Mobile device 900 still further comprises amodulator 914 and transmitter 916 that transmits a signal (e.g., powerlimitation indicators) to, for instance, a base station, another mobiledevice, etc. Although depicted as being separate from the processor 906,it is to be appreciated that power limit indicator 910, backoffevaluator 912 and/or modulator 914 can be part of processor 906 or anumber of processors (not shown).

FIG. 10 is an illustration of a system 1000 that facilitates reducingthe amount of feedback required to control forward link transmission ina MIMO system implementing a PGRC scheme. System 1000 comprises a basestation 1002 (e.g., access point, . . . ) with a receiver 1010 thatreceives signal(s) from one or more mobile devices 1004 through aplurality of receive antennas 1006, and a transmitter 1020 thattransmits to the one or more mobile devices 1004 through a transmitantenna 1008. Receiver 1010 can receive information from receiveantennas 1006 and is operatively associated with a demodulator 1012 thatdemodulates received information. Demodulated symbols are analyzed by aprocessor 1014 that can be similar to the processor described above withregard to FIG. 9, and which is coupled to a memory 1016 that storesinformation related to estimating a signal (e.g., pilot) strength and/orinterference strength, data to be transmitted to or received from mobiledevice(s) 1004 (or a disparate base station (not shown)), and/or anyother suitable information related to performing the various actions andfunctions set forth herein. Processor 1014 is further coupled to asubband selector 1018 that selects a subband. Subband selector 1018selects a subband based upon considerations of the power limitationindication of mobile devices and channel selectivity across subbands.

Subband selector 1018 is coupled to subband scheduler 1020. Subbandscheduler 1020 schedules mobile devices 1004 based upon consideration ofpower limitation information received from mobile devices 1004. Forexample, mobile devices with power limitations are schedules on innersubbands while mobile devices without power limitations are scheduled onportions of the remaining spectrum allocated. Modulator 1022 canmultiplex the control information for transmission by a transmitter 1024through antenna 1008 to mobile device(s) 1004. Mobile devices 1004 canbe similar to mobile device 900 described with reference to FIG. 9 andemploy the subband schedule to adjust power amplifier backoff. It shouldbe appreciated that other functions can be utilized in accordance withthe subject disclosure. Although depicted as being separate from theprocessor 1014, it is to be appreciated that subband selector 1018,subband scheduler 1020 and/or modulator 1022 can be part of processor1014 or a number of processors (not shown).

FIG. 11 shows an example wireless communication system 1100. Thewireless communication system 1100 depicts one base station 1110 and onemobile device 1150 for sake of brevity. However, it is to be appreciatedthat system 1100 can include more than one base station and/or more thanone mobile device, wherein additional base stations and/or mobiledevices can be substantially similar or different from example basestation 1110 and mobile device 1150 described below. In addition, it isto be appreciated that base station 1110 and/or mobile device 1150 canemploy the systems (FIGS. 1, 3-5 and 9-10) and/or methods (FIGS. 6-8)described herein to facilitate wireless communication there between.

At base station 1110, traffic data for a number of data streams isprovided from a data source 1112 to a transmit (TX) data processor 1114.According to an example, each data stream can be transmitted over arespective antenna. TX data processor 1114 formats, codes, andinterleaves the traffic data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing orthogonal frequency division multiplexing (OFDM) techniques.Additionally or alternatively, the pilot symbols can be frequencydivision multiplexed (FDM), time division multiplexed (TDM), or codedivision multiplexed (CDM). The pilot data is typically a known datapattern that is processed in a known manner and can be used at mobiledevice 1150 to estimate channel response. The multiplexed pilot andcoded data for each data stream can be modulated (e.g., symbol mapped)based on a particular modulation scheme (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected forthat data stream to provide modulation symbols. The data rate, coding,and modulation for each data stream can be determined by instructionsperformed or provided by processor 1130.

The modulation symbols for the data streams can be provided to a TX MIMOprocessor 1120, which can further process the modulation symbols (e.g.,for OFDM). TX MIMO processor 1120 then provides N_(T) modulation symbolstreams to N_(T) transceivers (TMTR/RCVR) 1122 a through 1122 t. Invarious embodiments, TX MIMO processor 1120 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transceiver 1022 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel.Further, N_(T) modulated signals from transceiver 1022 a through 1022 tare transmitted from N_(T) antennas 1024 a through 1024 t, respectively.

At mobile device 1150, the transmitted modulated signals are received byN_(R) antennas 1152 a through 1152 r and the received signal from eachantenna 1152 is provided to a respective transceiver (TMTR/RCVR) 1154 athrough 1154 r. Each transceiver 1154 conditions (e.g., filters,amplifies, and downconverts) a respective signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream.

An RX data processor 1160 can receive and process the N_(R) receivedsymbol streams from N_(R) transceivers 1154 based on a particularreceiver processing technique to provide N_(T) “detected” symbolstreams. RX data processor 1160 can demodulate, deinterleave, and decodeeach detected symbol stream to recover the traffic data for the datastream. The processing by RX data processor 1160 is complementary tothat performed by TX MIMO processor 1020 and TX data processor 1114 atbase station 1110.

A processor 1170 can periodically determine which precoding matrix toutilize as discussed above. Further, processor 1170 can formulate areverse link message comprising a matrix index portion and a rank valueportion.

The reverse link message can comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message can be processed by a TX data processor 1138, whichalso receives traffic data for a number of data streams from a datasource 1136, modulated by a modulator 1180, conditioned by transceivers1154 a through 1154 r, and transmitted back to base station 1110.

At base station 1110, the modulated signals from mobile device 1150 arereceived by antennas 1124, conditioned by transceivers 1122, demodulatedby a demodulator 1140, and processed by a RX data processor 1142 toextract the reverse link message transmitted by mobile device 1150.Further, processor 1130 can process the extracted message to determinewhich precoding matrix to use for determining the beamforming weights.

Processors 1130 and 1170 can direct (e.g., control, coordinate, manage,etc.) operation at base station 1110 and mobile device 1150,respectively. Respective processors 1130 and 1170 can be associated withmemory 1132 and 1172 that store program codes and data. Processors 1130and 1170 can also perform computations to derive frequency and impulseresponse estimates for the uplink and downlink, respectively.

It is to be understood that the embodiments described herein can beimplemented in hardware, software, firmware, middleware, microcode, orany combination thereof. For a hardware implementation, the processingunits can be implemented within one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described herein, or a combination thereof.

When the embodiments are implemented in software, firmware, middlewareor microcode, program code or code segments, they can be stored in amachine-readable medium, such as a storage component. A code segment canrepresent a procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment canbe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc. can be passed,forwarded, or transmitted using any suitable means including memorysharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The software codes can be storedin memory units and executed by processors. The memory unit can beimplemented within the processor or external to the processor, in whichcase it can be communicatively coupled to the processor via variousmeans as is known in the art.

With reference to FIG. 12, illustrated is a system 1200 that facilitatesgenerates an interference indication to be broadcasted to a plurality ofmobile devices. For example, system 1200 can reside at least partiallywithin a base station. It is to be appreciated that system 1200 isrepresented as including functional blocks, which can be functionalblocks that represent functions implemented by a processor, software, orcombination thereof (e.g., firmware). System 1200 includes a logicalgrouping 1202 of electrical components that can act in conjunction. Forinstance, logical grouping 1202 can include an electrical component forscheduling a first group of at least one mobile device on an innersubband of an allocated spectrum based at least in part on poweramplifier headroom information from the first group 1204. For instance,power limited mobile devices can be scheduled on inner subbands of anallocated spectrum. According to an example, the power amplifierheadroom information can comprise period information as well as staticdifferential information as described supra. Further, logical grouping1202 can comprise an electrical component for scheduling a subsequentgroup of at least one mobile device on a remaining portion of theallocated spectrum based at least in part on power amplifier headroominformation from the subsequent group 1206. For example, mobile deviceswithout power limitations can be assigned to remaining portion of theallocated spectrum after scheduling power limited mobile devices basedon the power amplifier headroom information as described. Moreover,logical grouping 1202 can include an electrical component for selectingsubbands based at least in part on power amplifier headroom information1208. According to an example, subbands can be selected based uponconsiderations of power limitations of mobile devices as well as channelselectivity across subbands. Additionally, system 1200 can include amemory 1210 that retains instructions for executing functions associatedwith electrical components 1204, 1206, and 1208. While shown as beingexternal to memory 1210, it is to be understood that one or more ofelectrical components 1204, 1206, and 1208 can exist within memory 1210.

Turning to FIG. 13, illustrated is a system 1300 that adjusts power on areverse link. System 1300 can reside within a mobile device, forinstance. As depicted, system 1300 includes functional blocks that canrepresent functions implemented by a processor, software, or combinationthereof (e.g., firmware). System 1300 includes a logical grouping 1302of electrical components that facilitate controlling forward linktransmission. Logical grouping 1302 can include an electrical componentfor transmitting a periodic power headroom measurement corresponding toa maximum achievable transmit power for a broadband assignment 1304. Forexample, periodic measurements can be made as a device moves throughouta service area, for example. Moreover, logical grouping 1302 can includean electrical component for advertising static differential powerheadroom corresponding to one or more points of interest 1206. Forexample, as described, the points of interest can include an innersubband, an edge subband, and/or a single base node. Thus, the periodicmeasurement can be added to one or more of the static differentialdynamics on a transmitting side to arrive at a computed power headroomfor selecting a subband. Additionally, system 1300 can include a memory1308 that retains instructions for executing functions associated withelectrical components 1304 and 1306. While shown as being external tomemory 1308, it is to be understood that electrical components 1304 and1306 can exist within memory 1308.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising” as “comprising”is interpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A method that facilitates dynamically adjustingpower amplifier backoff, comprising: transmitting a periodic powerheadroom measurement corresponding to a maximum achievable transmitpower; advertising static differential power headroom corresponding toone or more points of interest; and receiving a subband assignment. 2.The method of claim 1, wherein the points of interest comprise an innersubband, an edge subband, and/or a single base node.
 3. The method ofclaim 1, further comprising: evaluating a power amplifier backoff basedat least in part on the received subband assignment; and adjusting apower amplifier according to the evaluated backoff.
 4. The method ofclaim 3, wherein evaluating a power amplifier backoff comprisesdetermining a low backoff when the subband assignment indicatesallocation to an inner subband of allocated spectrum.
 5. The method ofclaim 3, wherein evaluating a power amplifier backoff comprisesdetermining a high backoff when the subband assignment indicatesallocation to an edge subband of allocated spectrum.
 6. A wirelesscommunications apparatus, comprising: at least one processor configuredto transmit a periodic power headroom measurement corresponding to amaximum achievable transmit power and advertise static differentialpower headroom corresponding to one or more points of interest; and amemory coupled to the at least one processor.
 7. The wirelesscommunications apparatus of claim 6, the at least one processor furtherconfigured to evaluate a power amplifier backoff based at least in parton a received subband assignment and change a power amplifier based uponthe evaluated backoff.
 8. The wireless communications apparatus of claim6, wherein the points of interest comprise an inner subband, an edgesubband, and/or a single base node.
 9. A wireless communicationsapparatus that mitigates non-linear distortion on spectral mask margin,comprising: means for transmitting a periodic power headroom measurementcorresponding to a maximum achievable transmit power for a broadbandassignment; and means for advertising static differential power headroomcorresponding to one or more points of interest.
 10. The wirelesscommunications apparatus 9, further comprising means for transmittingpower limitation information.
 11. The wireless communications apparatusof claim 9, wherein the points of interest comprise an inner subband, anedge subband, and/or a single base node.
 12. The wireless communicationsapparatus of claim 9, further comprising means for receiving a subbandassignment.
 13. The wireless communications apparatus of claim 12,further comprising: means for determining a power amplifier backoffbased at least in part on the received subband assignment; and means foradjusting a power amplifier according to the determined backoff.
 14. Thewireless communications apparatus of claim 13, wherein means fordetermining a power amplifier backoff comprises determining a lowbackoff when the subband assignment indicates allocation to an innersubband of allocated spectrum.
 15. The wireless communications apparatusof claim 13, wherein means for determining a power amplifier backoffcomprises determining a high backoff when the subband assignmentindicates allocation to an edge subband of allocated spectrum.
 16. Acomputer program product, comprising: a computer-readable medium,comprising: code for causing at least one computer to transmit aperiodic power headroom measurement corresponding to a maximumachievable transmit power; code for causing the at least one computer toadvertise static differential power headroom corresponding to one ormore points of interest; and code for causing the at least one computerto receive a subband assignment.
 17. The computer program product ofclaim 16, wherein the points of interest comprise an inner subband, anedge subband, and/or a single base node.
 18. A wireless communicationapparatus, comprising: a processor configured to: transmit a periodicpower headroom measurement corresponding to a maximum achievabletransmit power for a broadband assignment; and advertise staticdifferential power headroom corresponding to one or more points ofinterest; and a memory coupled to the processor.